A fuse or fuse element with indicators is illustrated by, means of the cartridge-type fuse disclosed within Gaia U.S. Pat. No. 4,058,784 , which has both a stationary current-conducting member and a movable current-conducting member, normally joined together by means of a connector, such as, for example, a mass of heat-softenable alloy. An indicator is connected to the movable member and has a spring, which can simultaneously move the movable member and indicator to a second position when the circuit-interrupter, that is, for example, the fuse, ruptures. In the illustrated embodiment, a small arm with a positive stop or knob is extended from the end of the cartridge under the biasing fuse of the spring at the time of the fuse-element rupture.
An elongated fuse or cartridge housing as disclosed within Urani U.S. Pat. No. 4,511,876 has a fusible wire disposed within the housing and is coupled to a spring indicator or terminal at one end and is secured to the opposite terminal end for conduction through the cartridge. The spring indicator unit is housed within one end of the cylindrical housing and biases the section of the ruptured fuse element connected to the indicator coil through the opening. Thus, fuse inoperability, and more specifically, an open circuit, is indicated.
Fahnoe U.S. Pat. No. 4,186,365 discloses a high-voltage fuse, which utilizes a movable component, such as, for example, an arcing rod, which is movable through an arc-extinguishing medium from a first and fuse-operable position to a second fuse-inoperable position. The fusible element arcing rod and arc-extinguishing medium are contained within a translucent insulative housing for the fuse. However, the condition of the fuse is difficult, if not impossible, to observe in either one of its blown or intact conditions from a position exterior to the fuse. Thus, a colored member is mounted for movement along with the arcing rod so as to provide a readily visible image through the translucent housing.
An electric fuse disposed within a tubular casing of insulating material in Link U.S. Pat. No. 4,323,874 has a pair of terminal caps mounted upon its ends so as to seal the tube. A fuse link connects the terminal caps and the fuse-link is embedded within an arc-quenching filler material disposed within the casing. A fuse indicator in an indicator housing is supported upon one of the end caps and has a spring-biased, pin-type indicator for piercing a cover plate at fuse rupture. The indicator is coupled to a pair of members of a non-conductive material, which members have a plurality of holes or notches with a fusible wire threaded through the holes so as to prevent relative movement between the members. One of the non-conductive members is supported by means of the housing and the other member is connected to the indicator for release of the movable member upon fusing of the wire connector and release of the indicator to its blown-fuse indicating position.
A delayed action indicator fuse is disclose within Goodwin U.S. Pat. No. 2,274,059 . This fuse is generally not responsive to transient, relatively low overloads, but requires continued overloads of a duration indicative of a defective line condition. The overload indicator disposed within an insulating cap is spring-biased so as to move a heating coil to fracture and move an indicator sign with the words, "no good", to a position opposite to a translucent window at the fuse end.
A low-voltage fuse with a blown-fuse indicator, shown within U.S. Pat. No. 3,783,428-Swain et al., has a molded insulating casing and a releasable plunger for indicating the blown-fuse condition. The indicator is recessed into the body of the casing and secured across the fuse structure by means of a fusible restraining wire. The indicator is biased and displaceable from the fuse body at upon rupture of the fuse element and release of the restraining wire. The indicator is displaced so as to provide maximum possible separation from the general structure of the fuse element, and thus eliminate potential arcing by means of the conductors.
Other indicating fuse structures are disclosed within U.S. Pat. No. 2,234,480-Schmidt; U.S. Pat. No. 1,337,357-Holdorf; U.S. Pat. No. 3,319,027-Hitchcock; U.S. Pat. No. 4,156,225-Cuzzone; and U.S. Pat. No. 4,023,133-Knapp, Jr., which patents generally provide an external indicator for indicating the blown-fuse condition. More specifically, in the above-noted patents only Schmidt-'480 discloses an internally retained fuse indicator disposed within a translucent window at the upper surface of the fuse, which indicator is spring-biased upwardly from the fuse base. The remaining patents disclose a physically displaceable indicator means secured within either the main body of the fuse or within an indicator retainer, which indicator is externally visible after the blown fuse condition occurs.